The invention generally relates to a protective mechanism and an optical coupler for use in systems for detecting the presence of hydrocarbons during mining or drilling operations. In the prior art, special optical couplers using Sylgard along with optical coupling oil have been employed with prior support systems to couple light from a scintillation element into a light detector device. Such an optical coupler is disclosed in U.S. Pat. No. 6,465,788, which is incorporated herein by reference in its entirety. One drawback to this approach is that, under some extreme cases of high loads, uneven loads, or high vibration, oil used in the optical coupling may migrate out over time and result in degraded detector performance. Another drawback is that precision fabrication and/or assembly tolerances must be maintained to prevent loss of oil and degraded performance. Yet another drawback is that particulate contamination of the optical coupler can also cause loss of oil and degraded performance.
Optical couplers made from self-wetting type materials (e.g., Wacker) have also been used. A drawback to these concepts is that the self-wetting materials exhibit viscous behavior and tend to flow outward from the optical interface, allowing the optical interface retaining force to be lost, and thus resulting in degraded performance.
Nuclear detectors, such as gamma detectors, have been used in mining applications and oil drilling operations for many years. In particular, gamma detectors have been used to measure the radiation that emanates from the formations surrounding the mining or drilling equipment. Such gamma detectors operate by utilizing the differences between the natural radioactivity of the target formation and the natural radioactivity of the adjacent formations to determine the boundaries between these formations.
Gamma detectors are sensitive and must be protected from harsh environments to survive and to produce accurate, noise free signals. This protection must include protection from physical shock and stress, including force, vibration, and abrasion, encountered during solid mineral mining and oil drilling operations. However, the closer in proximity the gamma detector is to the mineral being mined or drilled, the greater is the shock, vibration and stress to which the detector is subjected.
The presence of armor, which is required to protect the detector, further limits the available space. An explosion-proof housing takes up even more of the available space, and often results in reducing the diameter of the photomultiplier tube. When light detecting devices of relatively low mass density are used in connection with scintillation elements having a relatively high mass density, a specials means of support is needed to reduce rotation moments when under high vibration or high shock. Lower cost for providing protection for the detector is also needed.
A support system must be very effective in protecting the detector from the harsh vibrations and shock, but must also do so while consuming a small amount of space. Similarly, in mining operations, the outer portions of the detector and the armor must provide a high level of shielding from unwanted radiation and must protect the detector from impact and abrasion, all with a minimal use of space.
In the prior art, detectors have been protected by a plurality of springs which extended along the axial length of the detector or its scintillation element. An example of such a support system is a flexible dynamic housing, as disclosed in U.S. Pat. No. 6,452,163, which is incorporated by reference herein in its entirety. One drawback of such systems is that the springs extend along the axial length of the scintillation element and as such can block radiation from reaching the scintillation element. Another drawback is that such a mechanism uses a plurality of parts around the circumference of the detector. Moreover, the springs of the flexible housing have to be custom made for this specific industrial application. Also the annular gap that exists between the scintillation element and its rigid housing is not always uniform, such as because of dimensions of tolerance. This may complicate the installation or sizing of the system. Moreover, if the gap is not uniform, the dynamics of the system along the length may not be uniform or may be affected.
Another support mechanism for a detector is disclosed in pending application Ser. No. 10/270,148, which is incorporated herein by reference in its entirety. This type of support mechanism is a flexible support sleeve which extends along the length of the detector or scintillation element, and suffers from the same drawbacks discussed above with respect to the springs.
There remains a need for an optical coupling system that is less sensitive to fabrication/assembly tolerances, high/uneven loads, and high vibrations. There is also a need for a simplified, lower cost structure and method for supporting instrumentation packages and sensors, such as gamma detectors. A means for supporting sensitive elements, which have substantially a cylindrical shape, is needed to work in cooperation with other suitably chosen support elements. A more suitable method of supporting sensitive elements so as to produce less compression of optical reflecting material is also needed.